Surgeons use genetically engineered protein, titanium cages to stabilize vertebrae in lower back
A new type of spinal fusion surgery using genetically engineered protein to create new bone eliminates the need for painful bone graft harvesting and significantly improves patients' recovery time, according to spine surgeons at the University of Maryland Medical Center.
About 65 million people in the United States suffer from lower back pain, many as a result of degenerative disc disease in which the discs, or cushions, between the vertebrae start to deteriorate. More than 150,000 people undergo lumbar spinal fusions each year to help alleviate the pain. Surgeons traditionally use bone graft taken from a patient's hip and devices, such as metal cages, to build a bridge between the vertebrae, immobilizing a segment of the spine. The surgery is usually performed after physical therapy, anti-inflammatory medications, bracing and other more conservative treatments have failed.
"Removing pieces of bone from the hip for a graft is actually a lot more painful to many patients than the spine surgery itself, with 20 to 25 percent experiencing significant pain afterward. If they can avoid the additional surgery, they can recover faster, go back to work and get on with their lives much sooner," says Steven C. Ludwig, M.D., an orthopaedic/spine surgeon at the University of Maryland Medical Center who is on the faculty of the University of Maryland School of Medicine.
By using a genetically engineered protein as a bone-graft substitute, the surgery takes less time, is less painful and causes less blood loss, Dr. Ludwig says. Patients are able to go home the next day, instead of spending three to seven days in the hospital.
"This new technology is changing the way we perform spinal fusions," he says. "It is a less-invasive treatment option for some patients with degenerative disc disease struggling to cope with chronic, debilitating back and leg pain."
According to some estimates, 85 percent of the population has some disc degeneration by age 50. "As people get older, their discs start to wear out and lose hydration, causing pain in the lower spine. Genetics, smoking, lack of aerobic activity, obesity and previous surgery can all be factors," Dr. Ludwig says.
The U.S. Food and Drug Administration approved the use of recombinant human bone morphogenetic protein, or rhBMP-2, for certain types of spine fusion surgery in July. RhBMP-2 is a genetically engineered version of a naturally occurring protein that helps to stimulate bone growth, marketed by Medtronic Sofamor Danek, Inc. as InFUSE Bone Graft. The company also makes LT-CAGE, a thimble-like titanium cage also used in the procedure.
In the new technique, surgeons remove the remnants of the damaged disc and insert two metal cages into the space between the vertebrae. The rhBMP-2, a powder, is mixed with sterile water and then placed on a collagen sponge, which is inserted into the cages, where it helps to create new bone. "Over time, the bone grows through the metal cage, so the cage acts as a structural support. It seems to be the best way to get a solid, biological fusion," Dr. Ludwig says.
The fusion occurs as soon as six months with the protein, compared to 9 to 12 months with the bone graft harvested from the patient, Dr. Ludwig says. He calls rhBMP-2, which is also used to help promote healing of broken bones, "a very powerful agent."
Spinal fusions can be performed by accessing the spine from the front or back of the body, either through an "open" incision or laproscopically through several small incisions, but the FDA has only approved the new procedure for surgeries from the front. By operating from the front, surgeons avoid having to cut through muscle or possibly damaging nerves in patients' backs.
According to Dr. Ludwig, patients who have spinal fusions give up flexibility in their lower backs in order to reduce their pain and improve the overall quality of their lives. "By fusing the vertebrae, you are essentially putting a segment of the spine to rest permanently. So you are exchanging some motion for pain relief. It's kind of a give and take," he says.
"Patients can still exercise and be active after they have had the surgery," Dr. Ludwig says. "The whole goal is to improve their level of function and their level of pain relief."
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